In industry, CAD systems are used to aid in the design of an object by allowing designers to visualize and design the object before it is physically created. In this way, a designer may determine whether the three-dimensional modeled object is suitable for its intended application, and make necessary refinements, without having to resort to the expense of configuring equipment, making dies and acquiring the raw materials necessary to actually make the object.
When visualizing and designing the object, a user is often interested in viewing both internal and external portions of the object. In order to view these different portions concurrently, the CAD system removes, or clips, the portions of the object and renders the object as it would look without the removed portions. The portions designated for removal are known as clipping shapes. The removal of these clippings shapes is accomplished by generating a series of infinite clipping planes and dividing or clipping the object based on each clipping plane. The number of infinite clipping planes required depends upon the complexity of the clipping shape. As such, the object is rendered as clipped based on one or more infinite clipping planes. The object is then rendered as clipped again based on one or more remaining infinite clipping planes. Thus, the clipping and rendering of the object are performed in a single step. Once this process has been repeated for each set of infinite clipping plane, the resulting renderings of the object are merged to display the object.
Therefore, conventional rendering methods require that a plurality of renderings be performed for each clipping shape thereby resulting in an increased processing load to generate and display the clipped three-dimensional object. Further, the use of complex clipping shapes induces additional processing delays because of the repeated separate renderings. The conventional rendering methods also restrict a user to a limited amount of predefined clipping shapes because the clipping shapes are rendered with a specific rendering combination. These predefined rendering combinations further prevent the user from mixing a plurality of clipping shapes. In addition, repeated renderings of the object based on a clipping shape can cause effects such as transparency, reflection and shadows of the three-dimensional clipped scene to be rendered incorrectly.
A need exists for a method of rendering a three-dimensional modeled object as clipped without the complexity, processing load and other limitations that arise out of the conventional rendering method.